Tappet body and fuel injection pump comprising same

ABSTRACT

A tappet body for a fuel injection pump and a fuel injection pump, wherein the tappet body comprises: a first cavity, which is disposed at the bottom of the tappet body; a roller, which is held in the first cavity by a pin shaft in such a way that the roller is scrollable and axially movable; and a second cavity, which is disposed at the top of the tappet body and has an inner end face perpendicular to a longitudinal central axis of the tappet body; wherein at least one recess symmetrical about the longitudinal central axis of the tappet body is provided in the inner end face.

BACKGROUND OF THE INVENTION

The present application relates to a fuel feed system of an internal combustion engine, and in particular to a tappet body and a fuel injection pump comprising same.

Fuel feed systems of internal combustion engines are commonly known. A fuel feed system using a common rail system typically comprises a fuel injection pump device, a common rail system, and a plurality of fuel injection valves. Here, the fuel injection pump device is used for pumping fuel from a fuel tank and pressurizing the fuel to deliver same to the common rail system. The common rail system is used for storing high-pressure fuel from the fuel injection pump device. Each of the fuel injection valves is disposed within a corresponding one of a plurality of cylinders of an internal combustion engine such that the high-pressure fuel in the common rail system is fed to respective cylinders.

Referring to FIGS. 1, 2 and 3, a fuel injection pump device 1 in the prior art comprises a fuel injection pump 9. The existing fuel injection pump 9 comprises: a shell 19, which is formed with one upright hole 21 or two upright holes 21 arranged side by side and a chamber 28 in communication with the upright holes 21; plunger sleeves 13, which are assembled in the upright holes 21, wherein plungers 11 capable of moving in a reciprocating manner therein are respectively inserted in the plunger sleeves 13; and a camshaft 17, which is rotatably supported, wherein the camshaft 17 is formed with drive cams 25, 27 which correspond to the plungers 11 and are located in the chamber 28. A lower end of the plunger 11 is placed on a corresponding tappet body 15. A first cavity 29 is formed on the side of a tappet body 15 that faces the drive cam 25, 27. A roller 33 is held in the first cavity 29 by a pin shaft 31 which is mounted on the tappet body 15 in such a way that the roller is scrollable about the pin shaft 31 and axially movable along the pin shaft 31. A spring 35 and a spring seat 36 are further provided between the plunger sleeve 13 and the tappet body 15. A second cavity 30 is formed on the side of the tappet body 15 that is away from the drive cam 25, 27, and the spring seat 36 is accommodated within the second cavity 30. One side of the spring seat 36 is in contact with the spring 35, and the other side thereof is in contact with an inner end face 47 of the tappet body 15 (i.e., an inner end face of the second cavity 30). The spring 35 biases the tappet body 15 towards the camshaft 17 by the spring seat 36 such that the roller 33 is always in contact with corresponding drive cam 25, 27. In this way, when the camshaft 17 rotates, the plunger 11 moves in a reciprocating manner up and down against an outer contour of the drive cam 25, 27 by the roller 33 held on the tappet body 15 as a contour position of the drive cam 25, 27 changes.

However, in the process of moving up and down with the tappet body 15, due to inherent properties of a coil spring, repeated compression and elongation of the spring 35 may cause the spring to twist, generating a torque to the spring seat 36 and thereby generating a torque to the tappet body 15 by the friction between the spring seat 36 and the inner end face 47 of the tappet body 15. Since the inner end face 47 of the tappet body 15 is an annular plane disposed around a central protrusion 16, the contact area between the spring seat 36 and the inner end face 47 of the tappet body 15 is relatively large, so that the frictional force between them is also relatively large. As a result, left and right side end faces of the roller 33 of the tappet body 15 are twisted and thus come into contact with left and right inner side faces of the first cavity 29 of the tappet body 15, and friction is caused. Such friction may lead to wear of the left and right side end faces of the roller 33 and the left and right inner side faces of the first cavity 29 of the tappet body 15, which shortens the service life of the tappet body 15 and the roller 33 held on same.

SUMMARY OF THE INVENTION

Therefore, there is a need to improve the tappet body in the prior art.

An object of the present application is to overcome the above-mentioned defects in the prior art and to provide a tappet body and a fuel injection pump comprising same.

According to an aspect of the present application, provided is a tappet body for a fuel injection pump, the tappet body comprising: a first cavity, which is disposed at the bottom of the tappet body; a roller, which is held in the first cavity by a pin shaft in such a way that the roller is scrollable and axially movable; and a second cavity, which is disposed at the top of the tappet body and has an inner end face perpendicular to a longitudinal central axis of the tappet body; wherein at least one recess symmetrical about the longitudinal central axis of the tappet body is provided in the inner end face.

According to an embodiment, the at least one recess is an annular recess and is configured such that at least part of the recess is at a position of the inner end face that is proximate to an outer perimeter of the inner end face.

According to an embodiment, the distance between the at least part of the annular recess and the longitudinal central axis of the tappet body is greater than one third of the radius of the inner end face.

According to an embodiment, the at least one recess includes a plurality of radial recesses or dispersedly-arranged recesses and is configured such that at least part of the recesses is at a position of the inner end face that is proximate to an outer perimeter of the inner end face.

According to an embodiment, the distance between the at least part of the plurality of radial recesses or dispersedly-arranged recesses and the longitudinal central axis of the tappet body is greater than one third of the radius of the inner end face.

According to an embodiment, a central protrusion is further provided on the inner end face, and the at least one recess is disposed around the central protrusion.

According to an embodiment, a through hole for communication between the first cavity and the second cavity is provided in the tappet body, and the width of the at least one recess is greater than the diameter of the through hole.

According to another aspect of the present application, a fuel injection pump comprising the tappet body is provided.

According to an embodiment, the fuel injection pump further comprises:

-   -   an injection pump shell, which is formed with at least one         upright hole and a chamber in communication with the upright         hole, wherein the tappet body is disposed in the upright hole;

a plunger sleeve, which is fixedly assembled in the upright hole, wherein a plunger is inserted in the plunger sleeve, and the plunger is placed on the tappet body and is capable of moving in a reciprocating manner in the plunger sleeve;

a camshaft, which is rotatably supported by the injection pump shell, wherein the camshaft is formed with a drive cam which corresponds to the plunger and located in the chamber;

a spring and a spring seat, which are disposed between the plunger sleeve and the tappet body, the spring biasing a roller of the tappet body onto the drive cam by the spring seat; and

a fuel inlet and discharge valve assembly, which is disposed at an upper end of the plunger sleeve and is configured to allow fuel to be pumped into the fuel injection pump with the rotation of the camshaft and to further pressurize the fuel pumped into the fuel injection pump for ejection.

The positive effects of the present application are: the tappet body according to the present application can greatly reduce the contact area between the spring seat and the tappet body, thereby greatly reducing the wear, which is caused by friction, of left and right side end faces of the roller and left and right inner sides of the first cavity of the tappet body, and prolonging the service life of the tappet body and the roller held on same.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other aspects of the present application will be more fully understood from the following detailed description in combination with the following drawings. It is noted that the proportion in the drawings may be different for the purpose of clarity, but this does not affect the understanding of the present application. In the drawings:

FIG. 1 illustrates a longitudinal sectional view of a fuel injection pump device in the prior art for showing the structure in a pump body of a fuel injection pump;

FIGS. 2 and 3 respectively illustrate a partial cutaway perspective view and a sectional view of a tappet body in the prior art;

FIG. 4 illustrates a longitudinal sectional view of a fuel injection pump device according to an embodiment of the present application;

FIGS. 5 and 6 respectively illustrate a partial cutaway perspective view and a sectional view of a tappet body according to an embodiment of the present application.

In the figures of the present application, features with the same structures or similar functions are denoted by the same reference signs.

Description of Reference Signs: fuel injection pump device 1; vane pump 3; fuel metering unit 5; overflow valve 7; fuel injection pump 9; plunger 11; plunger sleeve 13; tappet body 15; central protrusion 16; camshaft 17; injection pump shell 19; injection pump shell component 19 a; injection pump shell component 19 b; upright hole 21; bearing 23; drive cams 25, 27; chamber 28; first cavity 29; second cavity 30; pin shaft 31; roller 33; spring 35; spring seat 36; fuel inlet and discharge valve assembly 37; recess 38; plunger chamber 39; valve holder 41; fuel injection channel 43; side end face 45; inner end face 47; through hole 48.

DETAILED DESCRIPTION

Preferred embodiments of the present application are described in detail below in combination with examples. It should be understood by those skilled in the art that the exemplary embodiments are not intended to limit the present application in any manner.

The structure and working process of the fuel injection pump device of the present application are generally described in combination with FIG. 4 below. As shown in FIG. 4, a fuel injection pump device 1 according to an embodiment of the present application generally comprises a vane pump 3, a fuel metering unit 5, an overflow valve 7 and a fuel injection pump 9 which are assembled together. The vane pump 3 pumps fuel from a fuel tank and delivers the fuel to the fuel metering unit 5. The fuel metering unit 5 can adjust the amount of fuel to be supplied to the fuel injection pump 9. The fuel supplied to the fuel injection pump 9 is pressurized and then ejected, so that the fuel flows to a common rail system. The fuel is then delivered from the common rail system to various fuel injection valves. In the case that the pressure of the fuel supplied to the fuel injection pump 9 exceeds a predetermined pressure, the overflow valve 7 can take an action to discharge part of the fuel from the fuel injection pump 9. In addition, the fuel injection pump device 1 can further comprise a relief valve for returning part of the fuel to the fuel tank.

The fuel injection pump 9 comprises two plungers 11, corresponding plunger sleeves 13, corresponding tappet bodies 15, and a camshaft 17. The camshaft 17 is supported on an injection pump shell 19 with one end of the camshaft 17 protruding through the injection pump shell 19 to receive a driving torque from an engine (not shown), so that the camshaft 17 rotates synchronously with the engine.

The injection pump shell 19 comprises an injection pump shell component 19 a and an injection pump shell component 19 b. The injection pump shell component 19 b and a vane pump shell are mounted to both ends of the injection pump shell component 19 a by bolts or similar devices. The camshaft 17 is rotatably held on the injection pump shell 19 by a bearing 23. Two upright holes 21 are formed in the injection pump shell component 19 a. Drive cams 25 and 27, which are respectively used for the respective plungers 11, are formed on the camshaft 17 and are located in a chamber 28, which is below the upright holes 21 and is formed within the injection pump shell component 19 a. It is noted that the injection pump shell component 19 a may also be formed with only one upright hole 21. The plunger sleeves 13 are fixedly assembled in the corresponding upright holes 21. The plungers 11 are respectively inserted in the plunger sleeves 13. A lower end of the plunger 11 is placed on the corresponding tappet body 15 so as to move in a reciprocating manner in the plunger sleeve 13. The specific structure of the tappet body 15 will be described in detail below in combination with FIGS. 5 and 6.

As shown in FIG. 4, a fuel inlet and discharge valve assembly 37 is provided at an upper end of the plunger sleeve 13. A plunger chamber 39 is formed between the fuel inlet and discharge valve assembly 37 and the respective plunger 11. A fuel injection channel 43 formed in a valve holder 41 is located above the fuel inlet and discharge valve assembly 37. The specific structure of the fuel inlet and discharge valve assembly 37 is commonly known in the art, and thus the detailed description thereof is omitted.

When one of the plungers moves downwards as a lobe position of one of the drive cams (e.g., the drive cam 27 in FIG. 4) changes, a negative pressure is formed in the plunger chamber 39 corresponding to the plunger, and the fuel inlet and discharge valve assembly 37 is closed in a commonly known manner to prevent backflow of the fuel from the common rail system. At the same time, the other plunger moves upwards as a lobe position of the other drive cam (e.g., the drive cam 25 in FIG. 4) changes, a positive pressure is formed in the plunger chamber 39 corresponding to the plunger, and the fuel inlet and discharge valve assembly 37 is opened in a commonly known manner so that the fuel is ejected from the fuel injection channel 43 and delivered to the common rail system. The process is performed alternately and repeatedly to continuously deliver the fuel to the common rail system.

Referring to FIGS. 5 and 6, which are respectively a partial cutaway perspective view and a sectional view of a tappet body according to an embodiment of the present application, wherein a roller is mounted in the tappet body. The tappet body 15 is substantially cylindrical in shape and has a longitudinal central axis. First cavities 29 are formed on the side of each of the tappet bodies 15 that faces the drive cams 25 and 27 (i.e., the bottom of each of the tappet bodies 15). Rollers 33 are held in the first cavities 29 by pin shafts 31 which are mounted on the tappet bodies 15 in such a way that the rollers are scrollable about the pin shafts 31 and axially movable along the pin shafts 31. Second cavities 30 are formed on the side of each of the tappet bodies 15 that is opposite the drive cams 25 and 27 (i.e., the top of each of the tappet bodies 15). Central protrusions 16 are provided within the second cavities 30. Inner end faces 47 perpendicular to longitudinal central axes of the tappet bodies 15 are formed around the central protrusions 16, wherein at least one recess 38 (e.g., annular recess) is formed in the inner end face 47 in such a way that the recess surrounds the central protrusion 16 and is symmetrical about the longitudinal central axis of the tappet body 15. Of course, the tappet body 15 may also be not provided with the central protrusion 16 so that the inner end face 47 is a generally circular surface.

As shown in FIG. 4, a spring 35 and a spring seat 36 are further provided between the plunger sleeve 13 and the tappet body 15. The spring seat 36 is accommodated within the second cavity 30, and one side of the spring seat 36 (i.e., an upper side) is in contact with the spring 35 and the other side (i.e., a lower side) is in contact with the inner end face 47 of the tappet body 15. The spring 35 biases the tappet body 15 towards the camshaft 17 by the spring seat 36 such that the rollers 33 are always in contact with corresponding drive cams 25 and 27. In this way, when the camshaft 17 rotates, the plungers 11 move in a reciprocating manner up and down against outer contours of the drive cams 25 and 27 by the rollers 33 held on the tappet bodies 15 as contour positions of the drive cams 25 and 27 change.

When the camshaft 17 rotates, the drive cams 25 and 27 drive the tappet body 15 to move up and down, thereby driving the plunger 11 and the plunger sleeve 13 to move up and down. Since the spring 35 is located between the spring seat 36 and the plunger sleeve 13, the spring 35 is compressed and elongated repeatedly. In the process that the spring 35 is compressed and elongated, the spring 35 generates a torque due to inherent properties thereof, which accordingly drives the spring seat 36 to twist. As described above, the lower side of the spring seat 36 is in contact with the inner end face 47 of the tappet body 15. The torque generated by the spring 35 is transmitted to the tappet body 15 by means of friction between the spring seat 36 and the tappet body 15, driving the tappet body 15 to twist. However, since the recess 38 is provided in the inner end face 47, only part of the lower side of the spring seat 36 is in contact with the inner end face 47, rather than all of the lower side of the spring seat 36 is in contact with the inner end face 47. As a result, the contact area between the spring seat 36 and the inner end face 47 of the tappet body 15 is greatly reduced and thus the frictional force between them is reduced, which mitigates the friction between left and right side end faces of the roller 33 of the tappet body 15 and the inner end face of the tappet body.

In the above example, the recess 38 is an annular recess and is configured such that at least part of the annular recess is at a position of the inner end face 47 proximate to an outer perimeter of the inner end face 47, i.e., the distance between the at least part of the annular recess and the longitudinal central axis of the tappet body 15 is greater than a half of the radius of the inner end face 47. This is because an annular contact part proximate to the outer perimeter of the inner end face 47 is often formed due to the contact between the lower side of the spring seat 36 and the inner end face 47. Hence, the contact area between the spring seat and the tappet body can be reduced provided that the recess 38 is disposed in the part of the inner end face 47 that is in contact with the spring seat 36. Furthermore, considering the moment caused by the frictional force, disposing the recess 38 at a position of the inner end face 47 that is proximate to the outer perimeter thereof can better reduce the torque transmitted to the tappet body. Preferably, the distance between the at least part of the annular recess and the longitudinal central axis of the tappet body 15 is greater than one third of the radius of the inner end face 47.

In another example, the recess 38 can include a plurality of radial recesses or dispersedly-arranged recesses, and is configured such that at least part of the plurality of radial recesses or dispersedly-arranged recesses is at the position of the inner end face 47 that is proximate to the outer perimeter of the inner end face 47, i.e., the distance between the at least part of the plurality of radial recesses or dispersedly-arranged recesses and the longitudinal central axis of the tappet body 15 is greater than a half of the radius of the inner end face 47. Preferably, the distance is greater than one third of the radius of the inner end face 47.

Furthermore, it is noted that a solution in which the position of the recess can be accordingly adjusted depending on different contact positions between the spring seat and the inner end face of the tappet body is envisaged in the present application.

As shown in FIGS. 5 and 6, the tappet body 15 can be further provided with at least two through holes 48 for communication between the first cavity 29 and the second cavity 30, so as to maintain the pressure balance between the two cavities. In this example, the width of the recess 38 can be greater than the diameter of the through hole 48 to reduce the contact area between the spring seat and the tappet body and to facilitate machining. A solution in which the width and depth of the recess 38 can be further adjusted according to the size of the tappet body and the spring seat is further envisaged in the present application, but is not described in further detail herein.

Therefore, by disposing the recess 38 in the inner end face 47 of the tappet body 15, the contact area between the spring seat and the tappet body can be greatly reduced, thus greatly reducing the wear, which is caused by friction, of the left and right side end faces of the roller and the left and right inner side faces of the first cavity of the tappet body, and prolonging the service life of the tappet body and the roller held on same.

Although the particular embodiments of the present application have been described above, it will be understood by those skilled in the art that the embodiments are merely illustrative and the protection scope of the present application is defined by the appended claims. Those skilled in the art could make various changes or modifications to these embodiments without departing from the principle and essence of the present application, and all these changes and modifications shall fall within the protection scope of the present application. 

1. A tappet body for a fuel injection pump, the tappet body (15) comprising: a first cavity (29), which is disposed at a bottom of the tappet body (15); a roller (33), which is held in the first cavity (29) by a pin shaft (31) in such a way that the roller is scrollable and axially movable; and a second cavity (30), which is disposed at a top of the tappet body (15), the second cavity (30) having an inner end face (47) perpendicular to a longitudinal central axis of the tappet body (15); wherein the inner end face (47) has therein at least one recess (38) symmetrical about the longitudinal central axis of the tappet body (15).
 2. The tappet body according to claim 1, wherein the at least one recess (38) is an annular recess and is configured such that at least part of the annular recess is at a position of the inner end face (47) that is proximate to an outer perimeter of the inner end face (47).
 3. The tappet body according to claim 2, wherein a distance between the at least part of the annular recess and the longitudinal central axis of the tappet body is greater than one third of a radius of the inner end face (47).
 4. The tappet body according to claim 1, wherein the at least one recess (38) includes a plurality of radial recesses or dispersedly-arranged recesses and is configured such that at least part of the recesses is at a position of the inner end face (47) that is proximate to an outer perimeter of the inner end face (47).
 5. The tappet body according to claim 4, wherein a distance between the at least part of the plurality of radial recesses or dispersedly-arranged recesses and the longitudinal central axis of the tappet body is greater than one third of the radius of the inner end face (47).
 6. The tappet body according to claim 1, wherein a central protrusion (16) is further provided on the inner end face (47), and the at least one recess (38) is disposed around the central protrusion (16).
 7. The tappet body according to claim 1, wherein a through hole (48) for communication between the first cavity (29) and the second cavity (30) is provided in the tappet body (15), and a width of the at least one recess (38) is greater than a diameter of the through hole (48).
 8. A fuel injection pump, comprising the tappet body (15) according to claim
 1. 9. The fuel injection pump according to claim 8, wherein the fuel injection pump further comprises: an injection pump shell (19), which is formed with at least one upright hole (21) and a chamber (28) in communication with the upright hole (21), wherein the tappet body (15) is disposed in the upright hole (21); a plunger sleeve (13), which is fixedly assembled in the upright hole (21), wherein a plunger (11) is inserted in the plunger sleeve (13), and the plunger (11) is placed on the tappet body (15) and is capable of moving in a reciprocating manner in the plunger sleeve (13); a camshaft (17), which is rotatably supported by the injection pump shell (19), wherein the camshaft (17) is formed with a drive cam (25, 27) which corresponds to the plunger (11) and located in the chamber (28); a spring (35) and a spring seat (36), which are disposed between the plunger sleeve (13) and the tappet body (15), the spring (35) biasing a roller (33) of the tappet body (15) onto the drive cam (25, 27) by the spring seat (36); and a fuel inlet and discharge valve assembly (37), which is disposed at an upper end of the plunger sleeve (13), the fuel inlet and discharge valve assembly (37) being configured to allow fuel to be pumped into the fuel injection pump with the rotation of the camshaft (17) and to further pressurize the fuel pumped into the fuel injection pump for ejection. 